Well, Kalindlara has the right of it.
(A) The Player's Guide is hoping to enthuse people to play, so I think is trying to spark imagination rather than often proscriptive advice. Reading a hundred and fifty "not this either" or "your character should be like this..." ins't going to encourage people. That said I think that this is exactly what it SHOULD be doing. If I'm trying to run a game for my tabletop group, I need them enthused!
(B) the Player's guide doesn't get updated as people discover new and terrible combinations.
(C) I've just seen a fair few concepts made for a PbP that my careful reading of the PG suggests might not be optimal. Possibly people just aren't getting it. It wasn't until I actually started thinking about my character as a GM might that I went "hell no!".
(D) Horror is an incredibly difficult genre to run, I have found. Cosmic horror even more so. People may need all the help they can get.
Totally not worth Paizo spending time on this, but it seemed something the community might want to think about.